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What's the difference between "IP-Based" and "Session-Based" Load Balance?

The video was presented by DrayTek Aust & NZ

For the routers with multiple WANs, there are two modes of load balance, IP-based and Session-based. In general, IP-based mode means if the destination is the same (e.g., the same server), the sessions will be routed through the same WAN interface; while Session-based allows sessions that have the same destination to be routed through different WAN.


Below we perform speed test to demonstrate the difference between the two modes.

(This setup applies to most of the models. For Vigor3900, Vigor2960 and Vigor300B, please refer to the article here.)

1. Suppose we have WAN1 which download/upload bandwidth is 10/10 Mbps, and WAN2 is 10/5 Mbps. First, make sure the WAN interfaces are active from Dashboard.


2. Set up IP-Based mode. Go to WAN >> General Setup, and select IP Based as Load Balance Mode


3. Run Speedtest to check the speed of each WAN. From the result, we can see the speed of each WAN interface is independent.


4. Set up Session-Based mode: Go to WAN >> General Setup, and select Session Based as Load Balance Mode


5. Run Speedtest again, from the results we can see now the speed is the sum of two WANs.


In summary, IP-based mode balances the connections between WANs, while one connection will use only one WAN interface, so the maximum throughput is limited by each WAN's bandwidth. On the other hand, Session-based mode combines the bandwidth of multiple WANs and brings higher throughput, which is good for FTP, HTTP, etc. However, please note that when one connection is balanced across multiple WAN interfaces, it might be rejected by some servers (e.g. HTTPS websites), which don't accept one connection from two different IP because of security concerns. In such cases, you may set up Route Policy to specify a WAN interface for the traffic destined to those websites.


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